ABSTRACTS OF PAPERS 59 



lows: (1) Corals have played a subordinate part, usually a negligible part, in 

 the building of the Floridian plateau; (2) every conspicuous development of 

 coral reefs or reef corals took place during subsidence; (3) in every instance 

 the coral reefs or reef corals have developed ou platform basements - which 

 owe their origin to geologic agencies other than those dependent on the pres- 

 ence of corals. 



The older Tertiary reefs and reef corals of Saint Bartholomew, Antigua, 

 and Anguilla all grew on subsiding basements. The relatively small propor- 

 tion of the contribution by corals to calcareous sediments in Florida, the 

 Bahamas, and the West Indies was shown. 



It was shown that the Floridian plateau was similar in configuration to the 

 Mo.squito bank off Nicaragua, to Campeche bank off Yucatan, and to Georges 

 bank oft" Massachusetts; the east side of the Floridian plateau is similar to 

 the continental shelf off Cape Hatteras. The platform which supports the 

 leef along the east coast of Florida extends beyond the reef limits northward 

 of Fowey Rock. The reef platform of the Great Barrier Reef of Australia is 

 similar to the continental shelf of eastern North and Central America, and it 

 continues south of the reef limits. Rosalind Bank, Caribbean Sea, was com- 

 pared with Rangiroa, Paumotus, which is similar in essential features. The 

 complex history of the coral-reef foundations in Florida, Antigua, Saint 

 Martin, Anguilla, and Bermuda was described, and it was stated that the 

 formation of the platforms could not be referred solely to Pleistocene time. 



Attention was directed to the facts that around the Island of Saba, in which 

 volcanic activity has so recently ceased that the crater is still preserved, there 

 was scarcely any platform at all ; that in the case of the young but slightly 

 older volcanic island of Saint Kitts, the platform was narrow, while the geo- 

 logically much older islands standing above the Antigua-Barbuda bank, the 

 Saint Martin plateau, and the Virgin bank rise above platforms which are 

 miles across and have an area many times greater than that of the present 

 land surfaces. Width of platform is therefoi'e indicative not of the amount of 

 submergence, but of the stage attained by planation processes. 



The conclusions were summarized as follows : 



1. Critical investigations of corals as constructional geologic agents are 

 bringing constantly increasing proof that they are not so important as was 

 long believed, and that many of the phenomena formerly attributed to them 

 must be accounted for by other agencies. Here it should be emphasized that 

 the ecology of probably no other group of marine organisms is known nearly 

 so thoroughly as that of corals. 



U. All known modern offsliore reefs which have been investigated gi'ow on 

 platforms which have been submerged in Recent geologic time. 



3. No evidence has as yet been presented to show that any barrier reef 

 began to form as a fringing reef ou a sloping shore and was converted into a 

 barrier by snlisidi-iicc ; Itut It is dear that many, if not all, barrier reefs stand 

 ou marginal plaLl'urms which alieady existed previous to Recent submergence 

 and the formation of the modern reefs. 



4. Study of the geologic history of coral-icrf i)I:itforms has estiddished tliat 

 there were platforms in early Tertiary time on the site of m:\uy of the present- 

 day platforms, and evidence has not as yet been adduciHl to ]lro^■e long -con- 

 tinuetl, uninterrupted subsidence in any coral-reef area. There have been 

 many oscillations of sealevel and Recent submergence is |>i<>l.alp!y lonipHcated 



